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This invention relates to magnesium halide compositions, catalysts made therefrom, methods of increasing the solubility of magnesium halides, methods of making magnesium halide compositions and catalysts, as well as methods of polymerization.
Solutions of MgCl2 in various electron donor solvents have found use in industry for the preparation of olefin polymerization catalysts. Often these solutions employ ethers, ketones and esters to form Mgxe2x80x94Ti catalyst precursors that have found wide acceptance in the catalysis of olefin polymerizations. Known precursors have resulted from the dissolution of magnesium chloride and titanium chloride in the solvent, followed by evaporation or distillation of the excess solvent. Tetrahydrofuran (TMF) has proven an especially useful solvent due to its coordinating properties with both MgCl2 and TiClx and its relatively low boiling point, which facilitates evaporation and solvent recovery. The resulting dried catalyst precursor is treated with a cocatalyst, typically an aluminum alkyl compound, to generate the composition which is active in olefin polymerization.
The use of such catalyst precursors in industrial polymerization processes exploit the solubility of MgCl2 in the solvent. Alkaline-earth halides are typically insoluble in hydrocarbon solvents However the solubility in certain coordinating electron donor solvents can be suitably high for industrial applications For instance, the solubility of MgCl2 in tetrahydrofuran (THF) increases from ca 0.2 M at xe2x88x9225xc2x0 C. to about 0.7 M at 30xc2x0 C. The amount of precursor that is obtainable per batch preparation of precursor is limited by the solubility of MgCl2.
Interestingly, however, at higher temperatures, the solubility of MgCl2 in such donor solvents decreases. For example, at the boiling point of THF (65xc2x0 C.) the solubility of MgCl2 is only about 0.4 M at atmospheric pressure. Such a reduction in solubility complicates the precursor drying process because removal of the solvent by heating is typically performed most effectively near the boiling point of the solvent. To avoid reducing the concentration of MgCl2 in the precursor solution to undesirable levels, the drying process is performed at reduced temperatures and pressures. Unfortunately, removal of the solvent under these conditions requires more time and is less effective, thereby reducing batch throughput.
The reduced solubility of MgCl2 at higher temperatures also causes the formation of a thick crust of precipitated MgCl2 on reactor walls and piping when solubility limits are exceeded at such temperatures.
For these reasons, catalyst precursor systems with improved solubility would find use in polymerization processes. Also, methods of increasing the solubility and changing the solubility profile of MgCl2 as a function of temperature would be useful. Therefore, magnesium halide catalyst components having higher solubility or a solubility that does not decrease with temperature and processes employing such catalyst components and catalysts made therefrom would be useful.
In some embodiments, there is provided a method for increasing the solubility of a magnesium halide, comprising 1) providing an electron donor solvent; contacting a magnesium halide with the electron donor solvent, and 2) providing an electron donor compound to form a magnesium-halide composition, wherein the composition is characterized by a solubility of the magnesium halide in the solvent that does not decrease as a function of the temperature up to the boiling point of the solvent
In other embodiments, a polymerization catalyst component comprising a magnesium halide, an electron donor solvent, and an electron donor compound, wherein the composition is characterized by a solubility in the electron donor solvent that does not decrease as a function of the temperature up to the boiling point of the electron donor solvent is provided.
In still other embodiments, a method of making a catalyst is disclosed In such embodiments, the method comprises forming a magnesium-containing composition, contacting the magnesium-containing composition with a transition metal compound to form a catalyst precursor, and contacting the catalyst precursor with a cocatalyst. The magnesium-containing composition includes a magnesium halide, an electron donor solvent, and an electron donor compound and is characterized by a solubility in the electron donor solvent that does not decrease as a function of the temperature up to the boiling point of the electron donor solvent.
Still other embodiments provide methods of making a polymer, comprising reacting at least one olefin monomer in the presence of a catalyst comprising the reaction product of: a magnesium-containing composition that includes a magnesium halide, an electron donor solvent, and an electron donor compound. The magnesium-containing composition is characterized by a solubility in the electron donor solvent that does not decrease as a function of the temperature up to the boiling point of the electron donor solvent. The catalyst composition also includes a transition metal compound, wherein the transition metal is selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, and combinations thereof, and a cocatalyst composition.
In some embodiments described above, compositions are substantially free of other electron donor compounds, and the molar ratio of the electron donor compound to magnesium halide is less than or equal to 1.9. In some embodiments, the ratio of the electron donor compound to magnesium halide is less than about 1.75, while in others the ratio of the electron donor compound to magnesium halide ranges from about 0.1 to less than about 0.5.
In some methods, catalyst precursors, catalyst components, and catalysts described herein, the magnesium halide is magnesium chloride, magnesium bromide, magnesium iodide, or combinations thereof. The electron donor compound may be a linear, branched, substituted, or unsubstituted aliphatic or aromatic alcohol having between one and about 25 carbon atoms. Exemplary alcohols include methanol, ethanol, propanol, isopropanol, butanol, 2-ethyl hexanol, 1-dodecanol, cyclohexanol, and di-tert-butyl phenol.
The solvent may be selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ethers, and aliphatic ketones. In some embodiments, the solvent is selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, ethers, and aliphatic ketones. Exemplary alkyl esters suitable as solvents include methyl acetate, ethyl acetate, ethyl propionate, methyl propionate, ethyl benzoate, and combinations thereof. Ethers that are suitable for use as the solvent include, but are not limited to, diethyl ether, diusopropyl ether, di-n-butyl ether, ethylisopropyl ether, methylbutyl ether, methylallyl ether, ethylvinyl ether, tetrahydrofuran, 2-methyl tetrahydrofuran and combinations thereof Suitable ketones include acetone, methylethyl ketone, cyclohexanone, cyclopentylmethyl ketone, 3-bromo-4-heptanone, 2-chlorocyclo-pentanone, allylmethyl ketone, and combinations thereof Of course, mixed solvents containing a second electron donor solvent that is an alkyl ester of an aliphatic or aromatic carboxylic acid, an aliphatic or cyclic ether, or an aliphatic ketone may be used in some embodiments. In some embodiments described herein, the solubility of a magnesium halide composition in solvent is greater than about 0.7 mol/liter.
In particular embodiments, the magnesium halide is magnesium chloride, the alcohol is ethanol or isopropanol, the molar ratio of the alcohol to magnesium is about 0.1 to about 1.1, the solubility of the magnesium halide or magnesium halide composition in the solvent is between about 0.8 and 2.5 mol MgCl2/liter.
Some embodiments provide a catalyst component comprises a composition of the formula
Mg(ED)rCl2[S]q, 
wherein r is greater than 0 and less than 1.9, and q is greater than 0 and less than 4.
Some catalyst precursors described herein include compositions comprising reaction product of or mixture of the magnesium-containing catalyst component with a solubility in the solvent that does not decrease with temperature up to the boiling point of the solvent and a second component comprising a transition metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, and combinations thereof. Some exemplary such second components include at least one titanium compound having a formula of Ti(ORxe2x80xa0)aXb, wherein Rxe2x80xa0 is Rxe2x80xa0, or CORxe2x80xa0, where Rxe2x80xa0, is individually a C1 to C14 aliphatic hydrocarbon radical or a C6 to C14 aromatic hydrocarbon radical; each X is individually Cl, Br, or I; a is 0 or 1; b is 2 to 4 inclusive; and a+b=3 or 4. In some embodiments, the at least one titanium compound comprises a titanium halide, such as, but not limited to, TiCl4, TiCl3, or aluminum reduced TiCl3.
In certain embodiments, catalyst precursor compositions comprise a composition of the formula
[Mg(ED)r]mTi(OR)nXp[S]q, 
wherein ED comprises a linear or branched alcohol having between one and about 25 carbon atoms; X is individually Cl, Br, or I; S is selected from the group consisting of alkyl esters of aliphatic and aromatic carboxylic acids, aliphatic ethers, cyclic ether, and aliphatic ketones, m ranges from 0.5 to 56; n is 0, 1, or 2; p ranges from 4 to 116; q ranges from 2 to 85, and r ranges from 0.1 to 1.9.
Some embodiments provide a catalyst that is the reaction product of a catalyst precursor and a cocatalyst. Other embodiments further include modifying the catalyst with a Lewis acid. Some suitable Lewis acids have the formula
Rg*MX3xe2x88x92g, 
wherein R* is a R*1 or OR*1; wherein R*1 is an aliphatic hydrocarbon having from 1 to 14 carbon atoms or an aromatic hydrocarbon radical containing from 6 to 14 carbon atoms; M is Al or B; X is Cl, Br, or I; and g ranges from 0 to 3. Exemplary chloride-based Lewis acids include tri-n-hexyl aluminum, triethyl aluminum, diethyl aluminum chloride, ethyl aluminum dichloride, trimethyl aluminum, dimethyl aluminum chloride, methyl aluminum, dichloride, triisobutyl aluminum, tri-n-butyl aluminum, diisobutyl aluminum chloride, isobutyl aluminum dichloride, ethoxy aluminum dichloride, phenyl aluminum dichloride, and phenoxy aluminum dichloride. Exemplary bromine-containing Lewis acids include diethyl aluminum bromide, ethyl aluminum dibromide, dimethyl aluminum bromide, methyl aluminum, dibromide, diisobutyl aluminum bromide, isobutyl aluminum dibromide, ethoxy aluminum dibromide, phenyl aluminum dibromide, and phenoxy aluminum dibromide Iodide-based Lewis acids include diethyl aluminum iodide, ethyl aluminum diiodide, trimethyl aluminum iodide, methyl aluminum, diiodide, diisobutyl aluminum iodide, isobutyl aluminum diiodide, ethoxy aluminum diiodide, phenyl aluminum diiodide, and phenoxy aluminum diiodide.
Other suitable Lewis acids include boron trichloride, boron tribromide, ethyl boron dichloride, ethoxy boron dichloride, diethoxy boron chloride, phenyl boron dichloride, phenoxy boron dichloride, diphenoxy boron chloride, (C6H13)BCl2, or (C6H13O)BCl2 
Still other suitable Lewis acids or cocatalysts follow the formula
AlXxe2x80x2d(Rxe2x80x3)cHe 
wherein Xxe2x80x2 is Cl or ORxe2x80x2xe2x80x3; Rxe2x80x3 and Rxe2x80x2xe2x80x3 are individually C1 to C14 saturated hydrocarbon radicals, d is 0 to 1.5; e is 0 or 1; and c+d+e=3. Exemplary such activators include Al(CH3)3, Al(C2H5)3, Al(C2H5)2Cl, Al(i-C4H9)3, Al(C2H5)1.5Cl1.5, Al(i-C4H9)2H, Al(C6H13)3, Al(C8H17)3, Al(C2H5)2H, Al(C2H5)2(OC2H5). In some embodiments one or more activators are present at an activator to transition metal compound ratio ranging from about 1 to about 400 moles of activator per mole transition metal compound. In some embodiments, the activator to transition metal compound ratio is about 4, about 10, about 15 or about 60 moles of activator per mole transition metal compound.
Some polymerization methods described herein provide polymers with a density ranging from about 0.88 to about 0.98 g/cm3. Some polymers have greater than or equal to about 90 mol percent ethylene and less than or equal to about 10 mol percent of one or more comonomers.